| Phosphorus as a substantial element in lake ecosystem,its occurrence,distribution and availability plays an important role on the eutrophication of lakes.In recent years,the water quality of Poyang Lake has entered a declining trend.Studying the behavior of phosphorus in the water and sediments of Poyang Lake is crucial to the protection of the lake water environment.Banghu lake is taken as the research object,collecting water and sediment samples from Banghu lake in different time and space.By means of chemical analysis method and SMT extraction method of sediment phosphorus morphology,studying the occurrence of phosphorus on overlying water and sediment,the spatial distribution characteristics were analyzed by using ArcGIS,as well as the bioavailability of phosphorus are analyzed.The correlation between bioavailable phosphorus and phosphorus forms and environmental factors in water was discussed.Effects of phosphorus forms in sediments on bioavailable phosphorus,and the release risk of phosphorus bioavailability in sediments was analyzed.The main conclusions are as follows:The TP content in the water of Banghu lake ranged from 0.040 to 0.283 mg/L during the wet season,PP was the dominated P form,accounting for 64.03% of TP content,and SRP content was the lowest,accounting for 13.80% of TP content.During the dry season,the TP content in the water ranged from 0.110 to 0.209 mg/L,PP accounted for 59.65% of TP,DOP accounted for 14.63% of TP,the range of 0.010 to 0.039 mg/L,which was the lowest.PP,DTP,DOP and SRP near the Ganjiang River and the confluence of Xiuhe River into the lake were higher than that in the other sections in wet season.During the dry season,the PP content showed that the content around the lake was higher than that in the middle of the lake,the distribution of DTP and SRP in the north lake area was higher than that in the south lake area,DOP concentration in the south lake area was higher than that in the north lake area,contrary to the distribution of SRP.The spatial distribution of phosphorus content in different forms was different,which was determined by the input of exogenous pollution,the unique hydrological characteristics of the Banghu Lake,terrain,and surrounding human activities.Estimation of bioavailable phosphorus in Banghu lake,the results showed that the BAP content in the water ranged from 0.019 to 0.148 mg/L,and the average content was 0.058mg/L in wet season.In dry season,the concentration of BAP in water ranged from 0.056 to 0.140 mg/L,and the average content was 0.094mg/L,which was higher than that in wet season.Through correlation analysis,the concentration of BAP with TP,DTP,SRP,DOP and PP has significant correlation,different forms of phosphorus have an impact on available phosphorus through various transformation effects.It was observed that the BAP concentration in the water accounted for more than 50% of TP,with 54.30% in wet season and 57.70% in dry season.The availability of various forms of phosphorus in water was different,and there were differences in the proportion of TP in each form of phosphorus in water,which implies that BAP could act as an indicator for lake eutrophic status more effectively and directly.The contents of total phosphorus in the sediments of Banghu ranged from 192.27 to 518.42 mg/kg,and IP was the main phosphorus form in Banghu Lake sediments,accounting for 66.17% of TP.The contents of NaOH-P were 92.59~367.78 mg/kg,accounting for 70.34% of IP,and NaOH-P was the main form of IP,mainly affected by industrial wastewater and domestic sewage discharge.HCl-P content were 23.04~111.55 mg/kg,accounting for 23.05% of IP,which is an important component of IP and was stability.The OP content were 71.14~264.47 mg/kg,accounting for 19.49%~50.00% of TP.The spatial distribution of phosphorus content in different forms was different,IP and NaOH-P in the sediments has trend of higher in the north lake area than that in the south lake area,mainly affected by the input of exogenous phosphorus.The spatial distribution of OP was relatively high in some region,mainly affected by the wilting of hydrophyte and non-point source agricultural pollution.The contents of AAP in the sediments of Banghu lake were 96.81~387.35 mg/kg,and the average content was 243.57mg/kg,accounting for 50.35% to 74.72% of TP.AAP in the sediments gradually decreased from northeast to southwest,AAP was enriched at the estuary of the lake,mainly affected by the input of exogenous phosphorus by the river and human activities.Through correlation analysis,the concentration of NaOH-P with AAP has significant correlation,and contributed the most to bioavailable phosphorus in the sediments.The concentration of AAP in the sediments of the Banghu Lake was lower than that in eutrophic lakes,but the proportion of AAP in TP was 61.34%,which was higher than that in eutrophic lakes,thus,the phosphorus in the sediments with high release potential.In order to effectively reduce the release risk of sediment phosphorus,sediment phosphorus control technique should focus not only on reducing the total phosphorus,but should also pay close attention to the removal and control of bioavailable phosphorus. |
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